A regulator of this kind introduces pressurized fluid from an inlet port and regulates the pressure thereof to a set point to discharge the fluid from an outlet port. One example thereof is disclosed in U.S. Pat. No. 5,458,001. The regulator comprises a valve seat disposed in a fluid flow path interconnecting the inlet port and the outlet port, a diaphragm movably disposed in the outlet side of the valve seat, a poppet valve connected to the diaphragm for opening and shutting the valve seat from the inlet side by movement of the diaphragm, and a pressure-adjusting spring for urging the diaphragm in the direction that the poppet valve opens the valve seat. The poppet valve opens and shuts the valve seat an amount corresponding to the opening of the acting force difference between the outlet side fluid pressure mutually inversely applied to the diaphragm and the pressure-adjusting spring force, so that the fluid pressure in the inlet side is reduced to be regulated at a set point.
In the above-mentioned regulator, the valve seat is attached to a body via a dish-shaped seat holder having a central hole being a fluid flow path and a recess portion around the central hole. That is: the seat holder in a state that the valve seat is fitted into the recess portion is placed on the body; a cap is attached on the body in that state; and the body and the cap are clamped together by a nut-type clamping ring, so that the outer peripheral portion of the seat holder is fixed between the body and the cap in a highly pressurized state while the valve seat is fitted between the seat holder and the body in a compressed state.
However, in the method of fitting the valve seat via the seat holder in a compressed state, the seat holder is prone to be deformed by a compressing reaction force of the valve seat because when the clamping ring is strongly clamped, the valve seat is also strongly compressed by the seat holder, so that when the deformation is excessive, hermeticity between the valve seat and the seat holder or the body is likely reduced.
Since between the body and the cap, not only the outer peripheral portion of the seat holder but also the outer peripheral portion of the diaphragm is simultaneously clamped in a hermetic state, it is necessary that thickness of the seat holder is controlled with a high degree of accuracy so that the clamping force to the diaphragm is not reduced by the interposition of the seat holder, requiring troublesome processing.